Planetary gear sets are well known. The basic planetary gear set includes a centrally located sun gear surrounded by a series of planetary gears that mesh with the sun gear. A ring gear meshes with the planetary gears. The sun gear is rotatably fixed to a shaft and rotation of the shaft drives the sun gear, which in turn drives the planetary gears, which drive the ring gear. Typically, the planetary gears are mounted to carrier shafts and are freely rotatable about their respective carrier shaft. The carrier shafts are either captured between a pair of carrier decks, thus enclosing the planetary gear set, or the carrier shafts extend from a single carrier deck. Generally, a bearing member is located between each planetary gear and the carrier shaft that carries the planetary gear.
When the planetary gear set is placed under torque, a load acts on the carrier shaft in a direction that is generally perpendicular to the longitudinal axis of the carrier shaft. This load causes wear of the bearing member and the carrier shaft. In planetary gear sets comprising only a single deck carrier wherein one end of the carrier shaft is free the load produced by torque causes a deflection of the carrier pin because the carrier shaft acts as a cantilevered member. This causes further wear of the bearing member and the carrier shaft.
Additionally, planetary gears are typically designed such that the teeth of the gear have a crowned shape to them. This crowned shape is necessary in order to aid in proper meshing of the planetary gear with the sun gear when the planetary gear system is under a torque load and also to keep the planetary gear centered on its carrier shaft. This crowning is difficult and expensive to use.
It would be advantageous to design a planetary gear set wherein the torque induced loads on the carrier shaft are reduced thus leading to a longer life of the carrier shaft and the planetary gear bearing member. In addition, it would be advantageous to produce such a planetary gear set that could be implemented using a single carrier deck. Finally, it would be advantageous to produce a planetary gear set that would permit a reduction in the crown on the teeth of the planetary gears while still maintaining the centering of the planetary gears on their carrier shafts.
The present invention is directed to overcoming one or more of the problems set forth above.